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Verilog · Beginners · After reading the verilog-newbie core source I finally understand the trade-offs

9
VEr/verilog-newbie·posted by slow_query·1 hour agoInternals

After reading the verilog-newbie core source I finally understand the trade-offs

Short version: verilog-newbie needs almost no tuning at small and medium scale — the point where it starts to hurt is much further out than most people assume. Full measurements below.

# Load test: do not jump straight to the max concurrency.
# Ramp it up, otherwise you miss the knee.
for c in 50 100 200 400 800; do
  wrk -t8 -c$c -d60s --latency http://127.0.0.1:8080/api/feed
  sleep 20
done

What genuinely surprised me was the tail. The average looked great while P99 jumped by an order of magnitude past some threshold. The cause was not verilog-newbie itself but our upstream connection reuse — the load test traffic was too clean and hid the long-tail requests.

On trade-offs, my view is this: if nobody on the team owns this area long-term, do not introduce a second mechanism. With two coexistence you first have to work out which one is even in play when things break, and that costs far more than the performance you saved.

Worth noting: the official docs do cover this, just in a very inconspicuous spot. I only found it reading the source comments, where the author explains the reasoning — roughly "so that it degrades into predictable behaviour in extreme cases".

3 comments

3 comments

M
Wwinter·just now

We have run this in production for two years without hitting it. That said, we never reached this scale, so our experience is not really evidence here.

441
Llinlin·3 minutes ago

Has anyone run a controlled experiment? I did, reducing it to a single variable, and the difference was 4% — within noise. So I suspect the main cause is something else.

427
Zzhu_zongOP·12 minutes agoedited

Worth learning from this debugging approach. We went straight at the logs and took a much longer route.

94

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